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Let's play a little word association. What athletes -- active or retired, living or gone home to glory -- come to mind when you read the following words?

Great.

MJ, Namath, Ruth, Montana. ...?

Cool.

Shaq. Johnny Damon. Ben Wallace. Bjorn Borg. ...?

Dominant.

Roger Clemens. Wilt Chamberlain. Tom Brady. Jim Brown. ...?

Exciting.

Dontrelle Willis. Manu Ginobli. Barry Sanders. Michael Vick. ...?

Revolutionary.

Hmm. Ali? No doubt. Jackie Robinson? Certainly. Billie Jean King. Absolutely. Arthur Ashe. No argument.

As we prepared to celebrate our nation's own revolutionary birth, my SI.com colleagues decided to compile a list of the Most Revolutionary Athletes. Our selections were limited to American citizens in deference to the holiday. That's why Liberian soccer player (and perhaps the country's future president) George Weah, China's Yao Ming and Brazil's Pele, all revolutionaries on any global list, are not included.

It was a stirring exercise, tossing about the names of athletes who, by some measure, have effected drastic change either in our games, in the way we think, or in our world. But as the names ricocheted around the room like pinballs we found ourselves struggling to justify including almost any of today's athletes.

Lance Armstrong? OK. LeBron James? Not yet. Barry Bonds? Holla back in a couple of years. Tony Hawk? Uh, are skateboarders athletes?

Talk about old-school values running head-on into new-school realities. Where are today's revolutionary athletes? Even scarier, Where are tomorrow's? Revolutionary is no small word.

Revolutionary is not to be taken lightly. Revolutionary is no joke. The word alone conjures images of myriad men and women in our history who risked their lives for a cause.

Few modern-era athletes have made such risks or, in some tragic cases, sacrifices. Some have risked their job. Others risked an endorsement deal. But only rarely has an athlete risked much more -- as when Robinson and Hank Aaron played despite threats to murder them as they stepped to the plate.

Pat Tillman is the most noted of many contemporary athletes who cast games aside and put their lives on the line for nothing more than what they believed. And yet sports has produced its own revolutionaries, athletes who stepped outside the safe boundaries, where only their performance mattered, and used their juice to instigate change. Or, simply, to change the way we think.

Initially, my mind rewound to an image of true sports revolutionaries: Brown, Cassius Clay, Bill Russell and Kareem Abdul-Jabbar are sitting at a table hosting a press conference. Behind them stand nine other black athletes, NFL stars such as Bobby Mitchell of the Redskins and the Packers' Willie Davis. All but one have donned a jacket and tie. They are gathered at a meeting of what is called the Negro Industrial and Economic Union to express their support for Clay's refusal to be inducted into the Army.